1. Field of the Invention
This invention relates generally to liquid formulations designed for application to substrates as coatings, printed patterns or the like, and is concerned in particular with a formulation comprising a mixture of a liquid and volatile viscosity altering components, the latter being substantially completely evaporative when the mixture is applied to a substrate and processed to its functionally dried state.
2. Description of the Prior Art
There are solutions and dispersions, which are used as coatings or printing inks that are best applied from a very dilute state, such as in a water or non-aqueous medium. In many cases, however, the rheology of these coatings or inks may cause them to flow too freely to allow for proper control of the amount of their application. Further, if discreetly applied, they may flow too freely to maintain their target positions.
There exists an abundance of rheology control agents, commonly referred to as “thickening agents”, which can be incorporated in the continuous liquid phase of a system to modify its viscosity to an appropriate level (i.e. one which meets the requirements of the application method). Unfortunately, when used in systems which are subsequently dried, the thickening agent left behind is often of a high enough concentration to adversely affect the performance of the coating or printing.
The printing of conductive inks and the application of optical coatings are two non-limiting examples where this dichotomy exists between the requirement of elevated viscosity for application purposes and purity in the functionally dried state. The dielectric properties of residual thickening agents can disadvantageously reduce the conductivity of conductive ink deposits, and the opacity of such residual thickening agents can introduce haze that adversely affects the desired clarity of optical coatings.
A need exists, therefore, for coating and ink formulations having rheologies that have been adjusted by the incorporation of thickening agents to achieve viscosities appropriate for the intended application modes, with the thickening agents being substantially completely removed from the resulting coating or ink deposits in their functionally dried states as applied to the substrates.
As herein employed, “functionally dried state” means that the volatile components of a liquid mixture have been evaporated to an extent sufficient to place the mixture in condition for its intended use.
Again, as herein employed, a component of a liquid mixture is considered to have been “substantially completely removed” when any residue of the component does not prevent the mixture, when in its functionally dried state, from performing its intended use.